Efficacy of Water-soluble Photoinitiator on the Adhesion of Composite Resin to Bovine Teeth in All-in-one Bonding System

The self-etching primer adhesives examined in the present study were aqueous mixtures of 30 wt% 2-methacryloyloxyethyl phenyl hydrogen phosphate, 35 wt% 2-hydroxyethyl methacrylate, and photoinitiator. For the photoinitiator, camphorquinone (CQ) or 2-hydroxyl-3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-N,N,N-trimethyl-1-propanaminium chloride (QTX) was used--where QTX is a unique water-soluble photoinitiator. The self-etching primer adhesive was applied directly to polished bovine dentin or enamel. Tensile bond strength of flowable composite resin to bovine teeth was measured after one-day immersion in water at 37 degrees C. The addition of QTX tended to increase tensile bond strength to dentin, whereby addition of 3 wt% of QTX produced the highest mean bond strength of approximately 10 MPa. CQ, on the other hand, did not show any efficacy in improving bond strength. For enamel bonding, there were no significant differences in bond strength between CQ and QTX. In conclusion, QTX was effective in improving the bond strength of composite resin to dentin in an all-in-one bonding system.